Recent advances in communications and in particular advances in the wireless delivery of services have been rapid. Long term evolution (“LTE”) of the third generation partnership project (“3GPP”), also referred to as 3GPP LTE, refers to research and development involving the 3GPP Release 8 and beyond, which is the name generally used to describe an ongoing effort across the industry aimed at identifying technologies and capabilities that can improve systems such as the universal mobile telecommunication system (“UMTS”). Radio access technologies (“RATs”) to serve the increasing need for mobile and broadband technologies continue to develop, such as LTE Advanced (“LTE-A”), 4G, WiMAX, in addition to older wireless technologies such as 3G and WiFi that are in widespread use.
As wireless communication systems such as cellular telephone, wireless data, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication devices transmitting a growing range of communication applications with fixed resources. The available frequency spectrum is a limited resource and the increases in the types and number of services offered, and the increase in users of these devices, have created a capacity limitation in many areas. Additional spectrum is clearly needed to expand the capacity of these systems for the demand now and also for future growth,
A recent development that offers additional spectrum for wireless communication systems in the United States is the transition to all digital television signals. Following the transition from analog over the air TV broadcasting to the all digital television broadcasts completed in 2009, a portion of the frequency spectrum previously allocated for analog television broadcasts became available. The Federal Communications Commission (“FCC”) has determined that the so-called “white space” spectrum or “WS” between licensed broadcast television stations and certain other licensed communications (certain medical devices, radio telescopes, wireless microphones and some other uses) that became available due to the transition to all digital TV broadcasts may now be used by unlicensed devices. The devices that use the television white space (“TVWS”) are required to comply with and follow certain guidelines created to prevent interference with licensed devices using channels in the spectrum. A report and order released by the FCC Nov. 18, 2008 provides the regulatory details, available from the FCC and numbered as “FCC 08-260”. This report is hereby incorporated by reference herein in its entirety.
The white space spectrum previously used for analog television broadcasts is considered especially important because this frequency spectrum, located below 1 GHz, has good range and other transmission characteristics that are especially attractive. In certain areas the need for wireless voice and wireless data communications services has, to date, been unmet. An example is in certain rural areas in the United States. It is expected that this newly available bandwidth may provide an opportunity to provide these services in these areas. Other areas where current broadband services are inadequate for the service demand are in very dense urban areas. This new spectrum may be used to provide additional signal capacity in those areas. As the amount of voice and data transmitted wirelessly increases and data intensive applications such as videoconferencing, video and movie broadcasts, interactive gaming, and the like become prevalent in wireless devices, and in particular in mobile wireless devices such as Personal Digital Assistant (“PDAs”) and advanced cellphones, the capability to use this new spectrum is expected to be very important.
The FCC has determined that two types of unlicensed devices may use the new spectrum in the “white space.” Fixed devices, base stations or access stations (“AS”), and portable or mobile station devices (“MS”) are both envisioned to use the spectrum. However, certain requirements are made to ensure that these new devices do not interfere with existing, licensed devices already using the spectrum. Licensed devices includes for example, broadcast television stations and wireless microphones. Wireless microphones are used, for example, in sports arenas, performance halls, theatres, television studios, and the like. Wireless microphones pose a particular challenge as they are not always in use and so not always present in the spectrum. They are also mobile devices.
The FCC regulations envision the unlicensed TV band devices (“TVBDs”) operating in several modes that are created so as to avoid this interference. As a first requirement, all unlicensed devices are required to use spectrum sensing to detect TV stations, wireless microphones, and other existing licensed or higher priority devices. The TVBDs are to stop transmitting within a short time of detecting a device where interference would otherwise occur. In addition, certain devices are master devices and certain devices are client devices. A client device only operates on channels and as enabled by a master device. A master device is one that, in addition to spectrum sensing, also is required to access a stored database of the location and channels of known licensed transmitter stations on a frequent basis. These devices also use geo-location or if fixed, an assigned location parameter to determine its own location, so that in accessing the database it can avoid transmitting on the spectrum when it is too close to a licensed device. Certain fixed stations may also initiate a network. Some personal/mobile stations operate with geo-location and spectrum sensing to avoid interference. In addition, some personal/mobile stations rely solely on spectrum sensing to avoid interference but do not use geo-location and database access.
FIG. 1 depicts the TVWS spectrum as presently provided in the United States. The shaded areas show the availability for unlicensed device operations. Channels 2-13 correspond to the TV channels 2-13, and these are Very High Frequency (“VHF”) bands. Channels 14-51 represent a portion of the Ultra-High Frequency (“UHF”) bands that were used as analog UHF channels. Each TV channel is 6 MHz wide, and thus the WS spectrum ranges from around 54 MHz to around 698 MHz. Certain channels are reserved, for example, 3, 4 and 37. As shown in the figure, certain channels below 20 are used only for fixed access station to other fixed station TV band devices (“TVBDs”). As shown in the figure, channels above 20 up to channel 51 are available for both fixed and personal or mobile stations that are TVBDs.
In order for the unlicensed users of the TVWS spectrum to operate without creating interference with existing transmissions such as digital TV broadcast stations, the FCC created mandatory guidelines for these new devices. All of the devices must perform spectrum sensing to sense licensed or other transmitters. Additional requirements depend on the device type. A “Mode I” device operates in client mode only, under the control of a master mode device. Because the master enables the Mode I device to transmit on certain channels, the Mode I device does not require geo-location service (such as Global Positioning System (“GPS”), for example) or access to the transmitter location data base. The Mode I device operates only on channels provided to it by a fixed access station, or by a Mode II TVBD. A “Mode II” personal/portable device is required to perform the location database queries, and, also to have geo-location. It may function as a master mode device and may perform network initiation. A “Special Mode” personal/portable device is authorized. These devices will not rely on database access or require geo-location. Instead these devices will rely on spectrum sensing to identify existing licensed transmitters such as TV broadcast transmitters, wireless mics, and other licensed transmitters. The FCC requires these devices to be tested and approved before use. These devices may act as a master mode device and may initiate a network.
Because the new requirements created by the FCC for implementing these devices requires that an unlicensed TVBD cease transmitting quickly (<2 s) when a licensed transmission is detected, methods and systems for implementing these devices in an efficient manner, including the capability to rapidly change channels within the TVWS to avoid interference, or to cease using the TVWS altogether, are needed. Therefore, what is needed in the art is a system and methods that provide optimal solutions for providing TV band devices that use the WS spectrum efficiently. Embodiments of the present invention address these needs.